Support is requested for a Keystone Symposia meeting entitled Dendritic Cells and Macrophages Reunited, organized by Jacques F. Banchereau and Siamon Gordon. The meeting will be held in Montreal, Quebec, Canada from March 8-13, 2015. Dendritic cells (DC) and macrophages are closely related myeloid cell types, serving as antigen-presenting and effector cells to initiate and regulate innate and adaptive immunity. They contribute to immune homeostasis and to disease pathogenesis during infection, inflammation and auto- immunity, providing targets for therapy. The fields of macrophage and dendritic cell biology diverged decades ago and have evolved in a relatively independent fashion. In particular, DC meetings are devoting considerable attention to adaptive immune responses while macrophage meetings focus on innate immunity. Yet, it is clear that both cell types share many common properties and eventually contribute to a protective immunity. The 2015 Keystone Symposia meeting on Dendritic Cells and Macrophages Reunited aims to reunite these two communities of investigators to emphasize common as well as distinctive cellular properties regarding both basic science and translation to human diseases. This meeting will be equally divided into basic biology and sessions dedicated to the importance of these cells in pathology including allergy, autoimmunity, cancer and infectious disease. The program will also emphasize the roles of dendritic cells and macrophages in human diseases.